The overall goal of this application is to explore the role of the membrane cytoskeleton in the functioning of photoreceptor outer segments. The membrane cytoskeleton decorates plasma membranes in essentially all cell types, providing them with mechanical support and retaining selected membrane proteins within specialized membrane sub-domains. Surprisingly, the role of the membrane cytoskeleton in photoreceptors had not been systematically addressed until very recently, when we reported that the outer segment targeting of the 2-subunit of the cyclic nucleotide-gated channel is critically dependent on its interaction with the membrane cytoskeleton protein ankyrin G. We now propose that another major function of ankyrin G is to retain this channel and other proteins at the rod outer segment plasma membrane and to prevent them from sorting into photoreceptor discs. In Aim 1 we will test this hypothesis for the case of the cyclic nucleotide-gated channel. In Aim 2 we will search for other ankyrin G binding partners in rod outer segments. We will also test whether selective plasma membrane localization of other proteins in rods is dependent on their binding to ankyrin G. We hope that the completion of this exploratory study will yield a sufficient body of information, concepts and experimental tools to build a larger program devoted to understanding the roles of the membrane cytoskeleton in photoreceptor health and disease. PUBLIC HEALTH RELEVANCE: The studies proposed in this application address the molecular and cellular mechanisms responsible for the biogenesis, maintenance and functioning of the light-sensitive compartment of the photoreceptor cells, the outer segment. Dysfunction of these processes causes some of the most severe types of inherited degenerative diseases of the retina, including but not limited to retinitis pigmentosa. This highlights the importance of understanding the mechanisms underlying the trafficking of proteins to the outer segment and their subsequent assembly into large functional complexes. Elucidating these mechanisms is essential for developing strategies for disease prevention and future therapeutic interventions.